Centrifuge and method for centrifuging a reaction vessel unit

ABSTRACT

A centrifuge for cleaning a reaction vessel unit, having a rotor for holding at least one reaction vessel unit with its opening(s) directed outwardly, a motor for rotating the rotor around a rotation axis, a housing having a substantially cylindrical inner surface, wherein a drain is provided for discharging fluid expelled from the reaction vessel unit, wherein a gap is provided between the inner surface and the rotor so that by rotating the rotor a wind is generated which drives the expelled fluid on the inner surface to the drain wherein an aspiration pump is connected to the drain for discharging fluid.

CROSS REFERENCE TO PRIOR APPLICATION

This application is a National Stage Patent Application of PCTInternational Patent Application Ser. No. PCT/EP2014/066947 (filed onAug. 6, 2014) under 35 U.S.C. § 371, which claims priority to EuropeanPatent Application Ser. No. EP13179437.2 (filed on Aug. 6, 2013),

which are all hereby incorporated by reference in their entireties.

The present invention relates to a centrifuge and a method forcentrifuging a reaction vessel unit.

US 2009/0181359 A1 discloses an automated immunoassay process having ahigh throughput and high sensitivity. As it is typical for immunoassayprocesses, a first specific binding member may react with a secondspecific binding member to form a complex wherein the concentration orthe amount of the complex is determined. This process uses magneticparticles to which one of the specific binding members is immobilized.An important step in the automated process is washing the complex whichis linked to the magnetic particles. The washing steps have a highimpact on throughput sensitivity, specificity, and cost of the wholeprocess. The less washing steps are needed, the faster the process is.The better the complexes are separated from non-specifically boundcomponents the better is the sensitivity of the process.

U.S. Pat. No. 8,329,475 B2 discloses a wash process for removingundesired components in samples which are to be analyzed. Therein it istaught to oscillate the level of a wash fluid in a container. Such acontainer can be configured as a cup, well, cuvette, test tube, etc. Bythe oscillating process small amounts of wash fluid are dispensed andremoved from the container. These amounts are smaller than the completeamount contained in the container. The oscillating action of the washfluid creates a moving meniscus. The moving meniscus reduces theconcentration gradient at the boundary layer of the container wall byconstantly refreshing the wash fluid at the surface on the containerwall.

Under the trade name SQUIRT™ a multi-format micro plate washer isavailable from the company matrical bioscience, USA. This washercomprises nozzles for squirting washing solution and air into thereaction vessels of microplates. Variable washing handles are provided.An automatic flipping element flips the micro plates so that a top-downwashing is carried out. This microplate washer is compatible betweendifferent SBS/ANSI micro-well plate formats (96, 384, 1536, etc.).

Washing devices which wash by dispensing and aspirating the washingsolution and/or air into and from reaction vessels cannot always removesuccessfully contaminating material that is present in the upper regionsof the reaction vessels, as it is difficult to direct the jet of washingsolution exactly adjacent to the upper boundary of the reaction vessel.Furthermore, there is a danger that the outer surface of the nozzles canbe contaminated, particularly when a top-down washing step is carriedout, wherein the nozzles are located below the reaction vessels. In thecase of a typical human diagnostics test the starting material will beplasma or serum. Proteins present in such material tend to formcomplexes. Clogging of proteins and subsequent failure of aspiration isa major drawback in conventional washer systems. It leads to failure inautomated systems and interruption of the total workflow in order togive chance for maintenance.

US 2009/0117620 A1 relates to a laboratory automation system that iscapable of carrying out clinical chemistry assays, immunoassays,amplification of nucleic acid assays, and any combination of theforegoing. In this system, micro-well plates and deep multi-well platesare used as reaction vessels. The use of such multi-well plates allowscarrying out immunoassays with a high throughput.

Other laboratory automation systems are using so called gel-cardsinstead of multi-well plates. The advantage of gel-cards in comparisonto multi-well plates is that they can be automatically opticallyanalyzed by scanning the side surfaces of the gel-cards. This allowsimplementing to analyze biological substances automatically byseparating them in the gel column.

EP 937 502 A2 discloses a method for handling a microplate in whichliquid is dosed into reaction vessels and the liquid is removed. Afterdosing the liquid into the reaction vessels the microplate iscentrifuged so that the centrifugal force is exerted towards the bottomof the reaction vessels and then the sample plate is centrifuged so thatthe centrifugal force is exerted away from the bottom of the reactionvessels to empty the reaction vessels.

JP 2009-264927 A discloses a microplate treatment device comprising arotating drum rotating around a horizontal rotation axis and havingholding sections on a side surface of the rotating drum which each canhold a microplate. The drum is surrounded by a cover. The microplatescan be placed in the drum so that the openings of the reaction vesselsface to the outside or face to the inside of the drum. From CN 102 175855 A a washer for enzyme-labeled pates is known, comprising a rotatingmechanism, a washing mechanism and a drainage mechanism. After thewashing is completed, a centrifugal force, generated by continuousrotation, can throw off the water remaining in holes of theenzyme-labeled plates, so that a drying effect is realized, thereforethe enzyme-level plates can be used at once after being washed.

U.S. Pat. No. 4,953,575 discloses a washing device for washing a cuvetteset. The cuvette set is placed into a holder in a rotor. The cuvettesare filled with the washing liquid. The washing liquid is removed fromthe cuvettes by rotating the rotor. The Italian patent application ITTO20 1 10 009 A relates to a centrifuge having a rotor. The rotorcomprises an elastic cable and a small piston which is actuated by theelastic cable. The reaction vessels can be pushed out of correspondingreceptions or cells during rotating of the rotor by means of the elasticcable and the small piston, wherein the reaction vessels are pushed inthe direction to the rotation axis. U.S. Pat. No. 5,419,871 pertains toan analyzer and an elevator for moving a slide element in a singlehorizontal plane, to one of plural incubators disposed at differentvertical levels. A drive mechanism is provided for raising and loweringthe elevator, and a pusher is provided such as a pusher blade within theelevator, to push a slide element from the distributor to a support inthe elevator, and then into one of the incubators.

U.S. Pat. No. 6,150,182 discloses a centrifuge for rotating a reactionvessel around a vertical axis. A magnetic element can be arranged in thevicinity of the reaction vessel so that the magnetic field supplied tothe reaction vessel for holding the magnetic beads in the reactionvessel.

WO 93/10455 A1 relates to a centrifuge vessel for performing automatedimmunoassays comprising a center tube, an outer waste chamber, and aplurality of micropartcle beads hosed within the center tube. The microparticle beads have a magnetizble core, which are acted upon an externalmagnetic source during washing operations.

From DE 10 2008 042 971 A1 a centrifuge is known for centrifuging areaction vessel so that more heavy components are collected in the lowersection of the reaction vessel. The lower section of the reaction vesselis surrounded by a magnetic element which holds magnetic beads for awhile after centrifuging in the lower section of the reaction vessel.

CN 102 417 902 A relates to a kit for extracting nucleic acid by amagnetic bead-microtiterplate method. US 2006/0198759 A1 discloses acentrifuge which can be used in a mixing mode for oscillating the rotorback and forth.

EP 1 952 890 A2 discloses a centrifuge adding a plurality of centrifugedisks. Each disk is embodied for attaching a gel-card and rotating thegel-card around a horizontal axis.

An object of the present invention is to provide a centrifuge forcleaning a reaction vessel unit.

This object is solved by the centrifuge procuring a reaction vessel unitas defined in claim 1. Preferred embodiments are defined in thecorresponding subclaims.

A centrifuge for cleaning a reaction vessel unit, having a rotor forholding at least one reaction vessel unit with its opening(s) directedoutwardly, a motor for rotating the rotor around a rotation axis, ahousing having preferably a substantially cylindrical inner surface,wherein a drain is provided for discharging fluid expelled from thereaction vessel unit, wherein a gap is provided between the innersurface and the rotor so that by rotating the rotor a wind is generatedwhich drives the expelled fluid on the inner surface to the drainwherein an aspiration pump is connected to the drain for dischargingfluid. An aspiration pump connected to the drain of the centrifugeallows a faster and improved clearing of the housing. This is importantfor avoiding cross-contaminations based on sample liquid present on thewalls and bottom of the housing of the centrifuge. By the connectedaspiration pump the liquid discharged from the reaction vessel(s) issucked immediately when the pump is switched on. The pump can either berunning during the centrifugation or switched on at any point of time asdesired. Any residual liquid remaining in the housing after switchingoff the aspiration pump can be removed manually. However, the main partwill already be removed by the pump and thus, decreases the risk of anycross-contamination enormously.

A centrifuge for cleaning a reaction vessel unit comprises

a rotor for holding at least one reaction vessel unit with itsopening(s) directed radially outwardly,

a motor for rotating the rotor around a rotation axis,

a housing having a substantially cylindrical inner surface surroundingthe rotor, wherein a drain is provided for discharging fluid expelledfrom the reaction vessel unit,

wherein a gap of not more than 1 mm is provided between the cylindricalinner surface and the rotor, so that by rotating the rotor a wind orcircular airstream is generated, which drives the expelled fluid on thecylindrical inner surface to the drain.

Due to the small gap between the rotor and the cylindrical inner surfacea strong circular air-stream is created by the rotating rotor, whichdrives the expelled fluid to the drain. Thus, it is possible to withdrawcompletely all liquid contained in the reaction vessel of the reactionvessel unit before rotating the rotor from the interior of the housing.This fluid is regarded as contaminating material. As this contaminatingmaterial can be completely be withdrawn, there is no danger ofcontamination. The gap is preferably not larger than 0.75 mm andparticularly not larger than 0.5 mm. The smaller the gap the stronger isthe circular airstream. However, this gap should preferably not besmaller than 0.1 mm and in particular not smaller than 0.2 mm or 0.3 mm,because such small gaps could cause the rotor to come into contact withthe cylindrical inner surface.

A further object of the present invention is to provide a centrifuge forcleaning a reaction vessel unit which can reliably clean reaction vesselunits containing volatile liquids. This object is solved by a centrifugefor cleaning a reaction vessel according to claim 3. Preferredembodiments are defined in the corresponding subclaims.

A centrifuge for cleaning a reaction vessel unit comprises

a rotor for holding at least one reaction vessel unit with itsopening(s) directed radially outwardly,

a motor for rotating the rotor around a rotation axis, and

a housing. A reaction vessel unit, such as a microtiter plate, can becleaned or processed in that the reaction vessel unit is rotated,wherein the openings of the reaction vessels of the reaction vessel unitare directed radially outwardly. Thus, the liquid contained in thereaction vessels is expelled. If the liquid is a volatile liquid, thenit is likely that a part of the liquid is vaporized. This vaporizedfluid can basically condense on a part of a reaction vessel unit and cancause a contamination.

For avoiding a contamination by condensation a cooling device isprovided for cooling an inner surface of the housing so that a vaporizedfluid is condensed on said inner surface and cannot condense on areaction vessel unit. By cooling the inner surface it can be securedthat volatile liquids are withdrawn from the gas atmosphere in thehousing so that they can be completely discharged from the housing.

The cooling device for cooling the inner surface of the housing ispreferably a Peltier element, particularly a Peltier foil, which coversthe outer surface of the housing.

The inner surface of the housing is preferably kept cooler than at least2° C. or 3° C. or at least even cooler than δ′O than the other parts inthe housing. A further object of the present invention is to provide acentrifuge for centrifuging a reaction vessel unit which can be easilyintegrated in an automatic labor robot or can be easily coupled to anexisting automatic labor robot.

This object is solved by a centrifuge according to claim 4. Advantageousembodiments are defined in the corresponding subclaims.

A centrifuge for centrifuging a reaction vessel unit comprises

a rotor for holding at least one reaction vessel unit with itsopening(s) directed radially outwardly and/or radially inwardly,

a motor for rotating the rotor around a rotation axis, wherein thesection in which the rotor is rotating forms a centrifuge section,

a loading mechanism for loading and unloading the centrifuge with areaction vessel unit, wherein the loading mechanism comprises a flexibleelongated beam for extension and retraction of a reaction vessel unitand a driving means for extending and retracting the beam, wherein theflexible elongate beam extends through the centrifuge section in itsextended state and is removed from the centrifuge section in itsretracted state so that the rotor can freely rotate.

This loading mechanism is rather simple and it can be integrated intothe centrifuge needing only a small insulation space. This loadingmechanism is embodied for horizontally moving a reaction vessel unit byextending or retracting the flexible elongated beam. Such a horizontalmovement can be easily combined with known handling devices forautomatic labor robots, because this loading mechanism extends into themoving range of the reaction vessel unit only horizontally so that itdoes not block the space above the moving range of the reaction vesselunit. This space can be completely be used by other parts of thecentrifuge or the automatic labor robot. Other known handling means haveusually parts being arranged above the moving range of a reaction vesselunit. Such parts could collide with other elements, particularly otherhandling means of an automatic labor robot.

The flexible elongated beam comprises preferably a magnetic coupling atits free end. Such a magnetic coupling can automatically couple to areaction vessel unit or a reaction vessel unit carrier having acorresponding counter coupling element. Preferably, the rotor comprisesa further magnetic coupling element which can hold the reaction vesselunit or the reaction vessel unit carrier by coupling the magneticcoupling of the rotor with the magnetic counter coupling element of thereaction vessel unit or the reaction vessel unit carrier.

The rotor comprises preferably a stopper for stopping the movement ofthe reaction vessel unit or the reaction vessel unit carrier when it isdrawn into the rotor by means of the beam, so that the beam isautomatically decoupled from the reaction vessel unit or the reactionvessel unit carrier, respectively.

The beam is preferably made of a bent metal sheet. The bent metal sheetis preferably bent into two strands or is winded-up on a reel.

The centrifuge according to any of the above described embodimentspreferably comprises a tempering means for tempering the gas containedinside the housing and/or tempering the rotor. This tempering means canadjust the temperature in a range with a minimum value of 0° C., 10^(<)€or 20^(<)€ and a maximum value of 40^(<)€, 60° C. or 80^(<)€. With sucha tempering means an incubation step can be carried out withoutunloading the reaction vessel unit from the centrifuge. A suitable rangeof temperature has to be selected according to the kind of a biologicalor chemical reaction which is to be carried out.

The housing comprises preferably an automatic door for loading andunloading the reaction vessel unit, wherein the door is opened formoving the reaction vessel unit into or out of the interior of thehousing or for exchanging the gas contained in the housing.

The centrifuge can be provided with a camera for scanning the reactionvessels of a reaction vessel unit. The camera can be placed with itsfield of vision directed to the bottom surfaces of the reaction vesselsor to the side surfaces of the reaction vessels. The reaction vesselunits, such as microtiter plates, comprising reaction vessels arrangedin a two-dimensional area are preferably scanned at the bottom surfaces.

A reaction vessel unit comprising several reaction vessels arranged inparallel in line, such as a gel-card, comprises preferable reactionvessels which are colored on one side and the reaction vessels are madeof a transparent material on the other side.

The colored side improves the contrast when the reaction vessels areoptically scanned at the transparent side.

The camera comprises preferably a light source, particularly astroboscopic light source. The above embodiments of the centrifuge arepreferably embodied so that the rotor is rotating about a horizontalrotating axis or a rotating axis which is oriented parallel to aplatform of the reaction vessel unit centrifuge, which is embodied forsupporting the reaction vessel unit centrifuge in accordance with itsdesignated use.

A further object of the present invention is to provide a multi-purposecentrifuge.

The object is solved by a centrifuge according to claim 13. Preferredembodiments are defined in the corresponding subclaims.

A centrifuge comprises a rotor for holding at least one reaction vesselunit with its opening(s) directed radially outwardly or radiallyinwardly,

a motor for rotating the rotor around a rotation axis,

a housing surrounding the rotor,

wherein the housing comprises two openings for loading and unloadingreaction vessel units, wherein the openings are arranged diametricallyopposite with respect to the rotation axis. Due to the two openings thecentrifuge can be loaded with a reaction vessel unit, wherein thereaction vessels are directed with the openings radially outwardly orradially inwardly with respect to the rotation axis without the need offlipping the reaction vessel unit before loading into the centrifuge.Such a centrifuge can be used for cleaning and washing on one hand orcentrifuging on the other hand. As there is no need for flipping thereaction vessel unit such a centrifuge can be easily integrated in anautomatic labor robot and providing both functions. According to afurther independent aspect of the present invention a centrifuge isprovided having

-   -   a rotor for holding at least one reaction vessel unit with its        opening(s) directed radially outwardly or radially inwardly with        respect to the rotation axis,    -   a motor for rotating the rotor around a rotation axis, and    -   a control unit for controlling a movement of the rotor forth and        back by a small angular distance of e.g. 5° to 20° for shaking        the reaction vessel unit. Such a shaking process can be used for        discharging the reaction vessels or for agitating the content in        the reaction vessels for supporting chemical and/or biological        reactions. The above described embodiments of a centrifuge are        preferably embodied so that the receptacle section is provided        for holding a reaction vessel unit so that the reaction vessels        are arranged substantially parallel to the rotation axis. Thus,        merely the same centrifuge force is exerted to all the sample        material. This applies for both a plurality of small reaction        vessels which are arranged substantially parallel to the        rotation axis as well as a large sample vessel such as a blood        bag which comprises its main extension in the direction parallel        to the rotation axis. Further examples of reaction vessels are        channels, tubes, bottles. The reaction vessels can be arranged        in microtiter plates, racks for carrying individual tubes or        other carriers for taking-up any kind of vessel, such as a blood        bag, or slides having structures for defining liquid spots        thereon. The receptacle section can be also embodied for holding        a plurality of reaction vessels, wherein several reaction        vessels are arranged in a substantially lateral direction to the        rotation axis. This is for example the case in a microtiter        plate, which comprises a plurality of rows with a large number        of reaction vessels and a plurality of columns with a smaller        number of reaction vessels. The rows are arranged parallel to        the rotation axis, wherein the columns are extending lateral to        the rotation axis. In such a case it is appropriate that the        reaction vessel unit is arranged in a distance to the rotation        axis which is substantially larger than the distance of the        lateral extension of the reaction vessel unit. The distance        between the rotation axis and the reaction vessel unit should be        at least as large as the lateral extension and preferably at        least 1.5, two times or three times as large as the lateral        extension of the reaction vessel unit. With such an arrangement,        it is also achieved that nearly the same centrifugal force is        exerted on all the samples contained in the different reaction        vessels. The lateral extension of the reaction vessel unit is        the distance between the center of two laterally outmost        reaction vessels.

A further advantage of a centrifuge with a horizontal rotation axis isthat it needs only a small space of a platform in comparison to acentrifuge having a vertical rotation axis which is perpendicular to theplatform.

Any of the above defined centrifuges can be combined with a dispensingdevice for automatically dispensing a fluid into the reaction vessels ofa reaction vessel unit. Such a dispensing device is preferably locatedin the neighboring of an opening for inserting a reaction vessel unitinto the centrifuge. The dispensing device can comprise one or moredispensing nozzles. Preferably the number of dispensing nozzles isadapted to the kind of reaction vessel unit which is used in thecentrifuge. The dispensing device is connected to a reservoir for adispensing solution, wherein a pump is provided for automaticallypumping the dispensing solution to the dispensing nozzles. Preferably, aheating device is provided in the reservoir for dispensing solution forheating the dispensing solution.

The centrifuge comprises preferably and additionally a loading mechanismwhich is embodied so that the reaction vessel units are moved below thedispensing device, so that with one dispensing nozzle several reactionvessels which are arranged in line of the moving direction of thereaction vessel unit can be consecutively filled with a dispensingfluid.

For washing magnetic beads the rotor of a centrifuge for cleaning andwashing reaction vessel units can be provided with a magnetic elementapplying a magnetic field to the reaction vessels, so that magneticbeads contained in the reaction vessels are hold in place by themagnetic field. The magnetic element can be integrated into the rotor,particularly in a base wall of the rotor, or can be part of a reactionvessel unit carrier. With such a magnetic element the magnetic beads canbe washed by centrifugation without losing the magnetic beads. Thecombination of using a centrifuge for washing and using such a magneticelement allows adjusting the speed of rotation so that all magneticbeads are kept in the reaction vessels during centrifugation.Furthermore, it is an object of the present invention to provide amethod for emptying a reaction vessel by centrifugation. This object issolved by a method, wherein a reaction vessel unit is placed in a rotorand, wherein the reaction vessel unit comprises at least one reactionvessel having an opening and the reaction vessel unit is placed with theopening of the reaction vessel radially outwardly for emptying thereaction vessel and the rotor is driven back and forth for shaking thereaction vessel unit.

After placing the at least one reaction vessel in the reaction vesselunit with the opening of the reaction vessel being placed radiallyoutwardly, the method comprises preferably three steps. Firstly, the atleast one reaction vessel is turned upside down by moving the rotorabout 180 degrees. The reaction vessel is thereby moved from a topmostposition in the centrifuge to a bottommost position. The speed for thishalf rotation is adjusted so that it is neither too slow nor too fast inorder to prevent any spillovers between the vessels. In case of a tooslow rotation speed sample liquid may pour from one vessel into anotheradjacent vessel. In case of a too fast rotation speed the sample liquidwill be ejected out of the vessels against the walls of the housing.Since at the beginning of the process the vessels are filled with a highvolume of sample liquid the liquid ejected against the walls of thehousing may splash back into the vessels or drop down into the vessels.However, by choosing the right speed for the half rotation, most of thesample liquid will basically fall out of the reaction vessel when turnedupside down and can easily be collected on the bottom of the housing. Toprevent any spillover effects the plate should be turned around with apreferred rotational speed of 0.2 to 1 second per 180 degrees.

In the second step the reaction vessel unit is shaken around thebottommost position by a control unit for controlling a movement of therotor forth and back by a small angular distance of e.g. 5° to 20°. Bythis shaking process sample liquid, which did not fall out during thefirst rotational step, will be discharged from the reaction vessel.

The third step comprises the centrifugation of the reaction vessel unitat a high speed (e.g. between 500 to 3500 rpm) in order to remove allresidual undesired sample liquid from the reaction vessel.

This method allows a quick and clear emptying of the reaction vesselwithout the risk of any spillover together with an easy collection ofthe discharged sample liquid. By only turning around the filled reactionvessel(s) for 180 degrees residual liquid will remain in the vessel dueto capillary forces. The shaking of the vessel(s) around the bottommostposition will help to overcome these forces and remove more of thesample liquid. However, even after the shaking step small amounts ofliquid might be held back in the vessel. These minimal amounts will thenbe removed by the final step of actual centrifugation at high speeds fora longer time between 2 seconds up to 1 minute clockwise and/orcounterclockwise. Thus, a completely dried reaction vessel will beobtained, whereby the liquid to be discharged is collected easily at thebottom of the housing of the centrifuge.

A further object of the present invention is to provide a method forparallel testing by means of gel separation, such as blood-typing,wherein a high throughput is achieved.

The object is solved by a method according to claim 15. The methodcomprises the following steps:

-   -   dispensing sample material in the regions into reaction vessels        arranged in a two dimensional array which are filled with gel,    -   centrifuging the array of reaction vessels, and    -   optical detecting the reaction vessels.

A microtiter plate comprises reaction vessels arranged in atwo-dimensional area. Thus it is possible to simultaneously test ahigher number of samples in comparison to reaction vessel units havingonly reaction vessels arranged in line.

The reaction vessels are optically detected, wherein it has been shownthat an optical detection with the field of vision from below or fromthe top onto the reaction vessels of the array of reaction vessels(microtiter plate) allows to reliably detecting whether the expectedresult is achieved. This method was used for blood-typing, whereinautomatically and reliably the blood types A, B and 0 could be detectedand distinguished.

Preferably, the optical detection is carried out from both sides frombelow and from the top onto the array of reaction vessels.

Additionally it is possible to automatically prepare the microtiterplates for such testing by means of gel separation in that

gel is filled into the reaction vessels of the microtiter plate, and

the microtiter plate is centrifuged so that the gel becomes free of airbubbles.

The centrifugation steps of this method are preferably carried out witha centrifuge as defined above. Instead of filling the reaction vesselswith gel, also a microtiter plate can be used comprising alreadygel-filled reaction vessels.

After dispensing sample material and reagents into the reaction vesselsonto the gel filling an incubation step can be carried out for keepingthe microtiter plate for a certain period of time at a predeterminedtemperature. Most preferably the microtiter plate is kept in thecentrifuge for carrying out this incubation step, wherein the centrifugecomprises a suitable tempering device. The centrifuge according to theinvention can be used for numerous kinds of assays. Examples of possibleassays are blood typing by means of microtiter plates, cellular assays,assays comprising magnetic beads, or PCRs with an oil overlay to ensurethe formation of two separate phases guaranteeing a full coverage of thevessel(s).

The present invention is a further development of the centrifugeaccording to PCT/EP2013/052356. PCT/EP2013/052356 is incorporated hereinby reference.

The present invention will be explained in greater detail below by meansof examples shown in the accompanying drawings. In the drawings:

FIG. 1 is a perspective view of a first example of a centrifugeaccording to the invention,

FIG. 2 is a perspective view of a rotor and a housing without front sidewall of the centrifuge according to FIG. 1,

FIG. 3 is a front view of the rotor and the housing without front sidewall,

FIG. 4 is a perspective view of a reaction vessel unit carrier,

FIG. 5 is a perspective view of the rotor containing a reaction vesselunit carrier and a reaction vessel unit,

FIG. 6 is a perspective view showing schematically a front platform, therotor and a loading mechanism,

FIG. 7 is a perspective view of the arrangement according to FIG. 6 inthe interface section between the rotor and the loading mechanism.

FIG. 8 is a perspective view of a second example of a centrifugeaccording to the invention,

FIG. 9 is a perspective view of the centrifuge according to FIG. 8without a housing,

FIG. 10 is a side view of the centrifuge according to FIG. 8 without ahousing,

FIG. 11 is a perspective view of a third example of a centrifugeaccording to the invention,

FIG. 12 is a perspective view of the centrifuge according to FIG. 11without a housing,

FIG. 13 is a side view of the centrifuge according to FIG. 11 without ahousing,

FIG. 14 is a perspective view of a further example of a centrifuge forcentrifuging gel cards, wherein the housing is partially cut out,

FIG. 15 shows one rotor and an automatic lid of the example according toFIG. 14, and

FIG. 16 is a perspective view of a reaction vessel unit carrier.

FIG. 17 shows an example for a possible experimental setup for an assaywith magnetic beads and magnetic rods for one reaction vessel

FIG. 18a-d shows different views of rods and pipetting tips for handlingthe rods as well as a microplate.

A first example of a centrifuge (FIG. 1-FIG. 7) is designed for cleaningand washing reaction vessel units. The reaction vessel units aremicrotiter plates 2. The microtiter plates 2 comprise a plurality ofreaction vessels 3 which are arranged in a two-dimensional array. Suchmicrotiter plates typically comprise 96, 384 or 1,536 reaction vessels3. The centrifuge 1 comprises a front platform 4, a centrifuge section 5and a driving section 6 (FIG. 1). The front platform 4 has, in the topview, a rectangular form which is slightly larger than a standardmicrotiter plate. Rims 7 are provided on all side edges of the frontplatform 4 except the one adjacent to the centrifuge section 5.

The centrifuge section 5 comprises a rotor 8 and a housing 9. The rotor8 is mounted on a horizontal shaft 10 (FIG. 2, 3). The rotor 8 comprisestwo receptacle sections each for receiving one microtiter plate 2. Thereceptacle sections are embodied as plate tray 11. The plate trays 11are each defined by a rectangular base wall 12 and two U-rails 13. EachU-rail 13 comprises a base shank 14 and a side shank 15 mounted on thebase wall 12 and a further side shank 16 being distant from the basewall 12. The base shanks 14 are arranged orthogonally to the base wall12 and the side shanks 15, 16 extend each from the base shank 14 in thedirection to the center of the rotor 8, so that the U-rails 13 arearranged opposite with their open sides.

The two base walls 12 of the two plate trays 11 are parallel to eachother, wherein central bores 17, through which the shaft 10 isextending, are provided in the section between the two base walls 12.The central bores 17 are arranged in the center of mass of the rotor 8.The center of the shaft 10 defines the rotation axis 18. The rotor 8 isembodied symmetrically with respect to the rotation axis 18. In thepresent embodiment the base walls 12, the U-rails 13 and the sections inbetween the base walls 12 are made from one single piece of aluminum.

On the front side of the rotor 8 the plate trays 11 are open so that amicrotiter plate can slide into the plate tray 11. At the rear side ofthe rotor 8 a stopper 19 is provided. The stopper 19 comprisespreferably a magnetic element.

The section in between the base walls 12 is cut out as far as possibleand bores are provided in the base walls 12 to minimize the moment ofinertia. In the present embodiment plate trays 11 are designed forreceiving a microtiter plate 2 together with a microtiter plate carrier20 (FIG. 4). The microtiter plate carrier 20 is a rectangular framehaving rims 21 at the side edges, wherein the inner surfaces of the rims21 define with a small play the position of a microtiter plate 2 on themicrotiter plate carrier 20. The upper surfaces of the rims are tiltedinwardly so that a microtiter plate is sliding into the section which isdefined by the rims 21

The microtiter plate carrier 20 comprises at one side edge a couplingelement made of magnetic material, particularly of a ferromagneticmaterial. This coupling element 22 can cooperate with the magneticstopper 19 and the rotor 8. The distance of the distant or outer sideshank 16 to the inner side shank 15 or the base wall 12 is so designedthat a microtiter plate 2 and a microtiter plate carrier 20 are held inradial direction with small play. This play is so that the microtiterplate carrier 20 and a microtiter plate 2 can be easily slid into andout of the plate tray 11. The outer side shanks 16 are so small thatthey do not cover any reaction vessel 3 of a microtiter plate 2.

The rotor 8 is surrounded by a housing 23. The housing 23 comprises acylindrical jacket wall 24, a front side wall 25 and a rear side wall 26(FIG. 1, 2). The jacket wall 24 comprises a lower and upper half shell27, 28, which are connected by outwardly arranged flanges 29. The innersurface of the jacket wall 24 is substantially in the form of a cylinderand arranged coaxially to the rotation axis 18. The interior space ofthe housing 23 defined by the jacket wall 24, the front side wall 25 andthe rear side wall 26 is called in the following as “rotor space” 56.

A drain 30 is provided in the lower section of the inner surface of thejacket wall 24. The drain is embodied in the form of a groove, whereinthe depth of the groove is continuously increasing in the direction tothe rear side of the housing 23 (FIG. 2). At the rear side of thehousing 23 an aspiration pump 73 (FIG. 3) is connected to the drain 30for discharging fluid from the housing 23. The drain 30 forms with theinner surface of the jacket wall 24 sharp edges.

A gap g between the radial outmost portions of the rotor 8 and the innersurface of the jacket wall 24 is preferably not larger than onemillimeter, particularly not larger than 0.75 millimeter and mostpreferably not larger than 0.5 millimeter. The smaller the gap is thestronger a circular airstream is generated when the rotor 8 is rotatingin the housing 23. However, this gap g should preferably not be smallerthan 0.1 millimeter and in particular not smaller than 0.2 millimeter or0.3 millimeter, because such small gaps could cause the rotor to comeinto contact with a fluid film on the inner surface of the jacket wall24. This is explained in further detail below.

The flanges 29 of the lower half shell 27 are connected to supports 31for fixing the housing 23 onto a platform (not shown). The front sidewall 25 comprises an opening 32 in the form of a rectangular slid. Anautomatic door is provided for closing the opening 32. The opening 32 isarranged in the level of the front platform 4. In the loading position,the rotor 8 is arranged horizontally with its base walls 12, wherein thebase wall of the upper plate tray 11 is arranged on the same level asthe front platform 4, so that a microtiter plate carrier 20 and amicrotiter plate 2 can slide horizontally from the front platform 4 intothe upper plate tray 11 and vice versa.

The driving section 6 comprises a motor (not shown) for rotating theshaft 10 and the rotor 8. The motor is connected to a control unit forcontrolling the rotation speed. The driving section 6 also comprises aloading mechanism 33 for loading and unloading the centrifuge 1 with areaction vessel unit, which, in the present embodiment, is a microtiterplate 2. The loading mechanism 33 comprises a flexible elongated beam 34for extension and retraction of a microtiter plate 2 or a microtiterplate carrier 20 together with a microtiter plate 2. The flexibleelongated beam 34 is made of a stripe of metal sheet which is slightlybent transverse to its longitudinal extension. Thus, the metal sheetprovides certain stiffness if it is extended linearly and on the otherhand it can be bent around an axis transverse to the longitudinalextension. Such bent metal sheet stripes are well known from metalmeasuring tapes.

In the present embodiment one end of the beam 34 is fixed on an innerwall 34 of the driving section 6, wherein the beam is extending from theinner wall 35 rearwards. The beam 34 is bent by a U-turn so that a freeend 36 of the beam is directed forwardly and the beam is extendingthrough a slid in the inner wall 35. Thus, the beam comprises an upperstrand 37 fixed to the inner wall 35 and a lower strand 38 extendingthrough the slid of the inner wall 35. The strand 38, which is extendingthrough the inner wall 35 and which comprises the free end 36, isclamped between two wheels 40, wherein one of the two wheels 40 isdriven by a stepper motor 41. Only one of the two wheels is shown in thedrawings. The free end 36 of the beam 34 is provided with a magneticelement 42. The beam 34 can be actuated by means of the stepper motor 41so that the free end 36 with its magnetic element 42 is extended ordriven through the centrifuge section 5 and through the opening 32 inthe front side wall 25. Thus, the free end 36 of the beam 34 reaches inthe maximum extended position the area of the front platform 4. In themaximum retracted position the free end 36 of the beam 34 is arrangedbehind the rotor 8 and particularly out of the centrifuge section 5, sothat the rotor 8 can be freely rotated.

The loading mechanism 33 can be coupled to a microtiter plate carrier20, which is placed on the front platform 4, just by extending the beam34 until the magnetic element 42 of the beam couples through thecoupling element 22 of the microtiter plate carrier 20. By retractingthe beam 34 the microtiter plate carrier 20 is drawn into one of theplate trays 11 of the rotor 8. When the microtiter plate carrier 20abuts to the stopper 19, the coupling between the magnetic element 42 ofthe beam 34 and the coupling element 22 of the microliter plate carrier20 is released by further retracting the beam and simultaneously thecoupling element 22 of the microtiter plate carrier 20 is coupled to themagnetic element of the stopper 19 and thus fixed in position in therotor 8.

This loading mechanism 33 allows coupling the centrifuge 1 to anytransport system for transporting microtiter plates in an automaticlabor robot. The labor robot just has to put a microtiter plate 2 onto amicrotiter plate carrier 20 located at the front platform 4. Then theloading mechanism 33 can load and unload the rotor 8. It is alsopossible to place the centrifuge 1 without a front plate directlyadjacent to a transport belt for transporting microtiter plates, whereinmicrotiter plates 2 can be withdrawn from the transport belt with theloading mechanism 33 and can be put onto the transport belt again. Inthe present embodiment a microtiter plate carrier 20 having a couplingelement 22 is used. It is also possible to provide the microtiter plates2 with such coupling elements 22 so that there is no need for amicrotiter plate carrier. A further advantage is that the loadingmechanism 33 is placed on the rear side of the centrifuge section 5 sothat the centrifuge 1 can be coupled to an existing laboratory robotwithout any intermediate devices. This facilitates the integration ofthe centrifuge into the existing laboratory robots. Furthermore, theloading mechanism 33 needs only a small installation space. Thisinstallation space can even further be reduced if the beam is winded upon a reel instead of bending it into two strands.

The centrifuge 1 is used for cleaning microtiter plates 2. A microtiterplate 2 containing liquid in the reaction vessels 3 is put on amicrotiter plate carrier 20 which is located on the front platform 4.The microtiter plate carrier 20 is drawn together with the microtiterplate 2 into one of the plate trays 11 by means of the loading mechanism33. The microtiter plate carrier 20 is magnetically coupled to thestopper 19. The rotor is rotated, wherein the rotation speed iscontrolled by a control unit in a range of 5-3,000 RPM. Due to thecentrifugal force, the liquid is expelled from the reaction vessels 3.By this centrifugal washing it is possible to reliably remove liquideven from small reaction vessels, in which capillary forces occur.Therefore, liquid can be reliably removed from microtiter plates having384 or 1,536 reaction vessels.

During the centrifugation the liquid is expelled from the reactionvessels 3 and drops of the liquid are impinged on the inner surface ofthe jacket wall 24. The drops form a liquid film on the inner surface ofthe jacket wall 24. Due to the rotation of the rotor 8 and the small gapbetween the rotor 8 and the inner surface of the jacket wall 24, astrong rotational airstream is caused, which forces the liquid film onthe inner surface of the jacket wall 24 to flow in the rotationaldirection of the rotor. Thus, the liquid is driven to the drain 30, fromwhich the liquid is withdrawn by means of the aspiration pump.

For reliably withdrawing the liquid from the internal space of thehousing 23, the rotation speed is preferably at least 500 RPM,particularly at least 1,000 RPM and most preferably at least 1,500 RPM.The rotation speed should be adjusted in dependence on the surfacetension of the liquid and the gap between the rotor 8 and the jacketwall 24.

Preferably the rotational direction is reversed at the end of thecentrifuging step so that a liquid film on the inner surface of thejacket wall 24 on the rear side of the drain 30 with respect to thefirst rotational direction is driven into the drain 30 by rotating therotor 8 with a second rotational direction. It has been shown that theresidual volume of the liquid, which remained in a reaction vessel aftercentrifuging a microtiter plate, was smaller than 0.01 μl applying anamount of liquid of e.g. 200 μl. The liquid can be a washing solution,so that with one washing step a dilution ratio of 20,000:1 is achieved.Ordinary washing machines for washing microtiter plates provide adilution ratio of 40:1. Using such a centrifuge increases the dilutionratio 5,000 times.

Microtiter plates with coated reaction vessels are used for immunoassayprocesses. With the coating, a first specific binding member isimmobilized in the reaction vessel. In typical immunoassay processes,such as ELISA, a second specific binding member forms a complex with thefirst specific immobilized binding member. Non-specifically boundcomponents have to be removed from the reaction vessels. With thecentrifuge 1 this can be achieved in a low number of washing steps bydispensing a certain washing solution into the reaction vessel 3,centrifuging the microtiter plate and eventually repeating the washingstep. If microtiter plates with large reaction vessels are used, such asstandard microtiter plates having 96 reaction vessels, it can beadvantageous if at the beginning the rotor is only rotated once by 180°,so that the openings of the reaction vessels 3 are directed downwards. Alarge amount of the liquid is then flowing out of the reaction vessels.This can be supported by a shaking movement of the microtiter plate,wherein the rotor is moved forth and back by a small angular distance ofe.g. 5° to 20°.

It is also known to immobilize a first specific binding member onmagnetic beads. The magnetic beads can be put into reaction vessels of amicrotiter plate, wherein the immunoassay (Enzyme Immuno assay, EIA;Chemiluminescent Immuno Assay, CLIA) processes can be carried out. Inany case, these magnetic beads have to be washed.

The difference in the efficiency of washing of beads or other solidsurfaces is dependent on the number of washing steps needed. A typicalhigh sensitivity assay (e.g. by the technology of the company Quanterix,USA) requires up to 12 subsequent washing steps because the residualvolume has to be diluted by a factor of more than 10⁸ (N). Washing bycentrifugation leads to a substantial improvement of assay workflow bycutting the number of washing steps drastically.

For washing magnetic beads a microtiter plate carrier 20 (FIG. 16) isprovided comprising a plate having a number of magnetic elements 57. Thenumber can be one for one big magnet covering the plate area or morethan one, wherein the magnetic elements are regularly distributed onsaid plate. These magnetic elements 57 apply a magnetic field to thereaction vessels. During the washing step, the rotational speed of thecentrifuge is to be adjusted that the centrifugal force exerted onto themagnetic beads is smaller than the magnetic force between the magneticbeads and the magnetic elements of the microtiter plate carrier. Boththe magnetic force and the centrifugal force depend on the size andmaterial of the magnetic beads. It has been shown that it is reliablypossible to wash magnetic beads without losing any magnetic bead. In acalibration step, magnetic beads contained in the liquid that iswithdrawn by the aspiration pump from the rotor space 56 are detected,wherein the rotation speed is gradually increased. This can be done bymeans of a magnetic sensor, such as a hall sensor located adjacent tothe outlet of the drain 30. After detecting a magnetic bead in theliquid, the actual rotation speed is captured and reduced by a certain,small predetermined amount. This rotation speed is used in thesubsequent washing steps for washing magnetic beads.

The above explained first example of a centrifuge 1 comprises preferablya cylindrical jacket wall 24, which is made of a thermal conductingmaterial, such as aluminum. The jacket wall can be provided with thecooling means, so that the inner surface of the jacket wall 24 can becooled. The inner surface of the jacket wall 24 is preferably keptcooler than the rotor 8 and any other part inside the jacket wall 24.Thereby it is secured that fluid condenses only on the inner surface ofthe jacket wall 24 and not on the rotor 8 or any other part. The fluidcondensed on the inner surface of the jacket wall 24 is securelydischarged via the drain 30 from the housing 23, as described above.Preferably, the inner surface of the jacket wall 24 is kept cooler thanat least 2° C. or 3° C. or even cooler than δ′O than the other partsinside the rotor space 56 and/or cooler than the gas contained in therotor space 56, so that fluid originating from the liquid in thereaction vessels, which is vaporized into the gas contained in the rotorspace is recondensed only on the inner surface of the jacket wall 24. Bycooling the jacket wall 24, it can be secured that volatile liquids arewithdrawn from the gas atmosphere in the housing 23 and completelydischarged from the housing 23.

The cooling means for cooling the jacket wall 24 is preferably a Peltierelement, particularly a Peltier foil, which covers the outer surface ofthe jacket wall 24. Such a Peltier element conveys the heat of thejacket wall 24 radially outward. Thus, the inner surface of the jacketwall 24 is kept cool and the outer side of the Peltier element is warm.Therefore, condensing of fluid appears only on the inner surface of thejacket wall 24 and not in any other part of the centrifuge.

The centrifuge 1 can comprise a venting system for exchanging the gas orair, respectively in the rotor space 56. The venting system comprises ablower coupled to an opening e.g. in the rear side wall 26. When theopening 32 in the front side wall 25 is opened, the air in the rotorspace 56 can be exchanged by activating the blower. The exchange of thegas or air is usually carried out between two consecutive centrifugingprocesses. The venting system can also be combined with aheating/cooling device so that the air introduced into the rotor space56 is heated or cooled. Such a venting system forms a tempering devicefor tempering the interior of the rotor space 56 to a predeterminedtemperature.

A second example of a centrifuge (FIG. 8-FIG. 10) is designed forcentrifuging reaction vessel units. The reaction vessel units aremicrotiter plates 2. The second example of the centrifuge 1 is similarlyembodied as the first example so that similar parts are designated withthe same reference signs. These parts are identical to the ones of thefirst example, as far as there is no different explanation. Thiscentrifuge 1 comprises a front platform 4, a centrifuge section 5 and adriving section 6 (FIG. 9). The centrifuge section 5 comprises a rotor 8which is mounted on a horizontal shaft 10 (FIG. 9). The rotor comprisesone receptacle section or plate tray 11 for receiving one microliterplate 2. The plate tray 11 is defined by a rectangular base wall 12 andtwo U-rails 13. The base wall 12 is connected by means of legs 43 with aflange 44 defining a central bore 17 through which the shaft 10 isextending. In the second example, the distance between the base wall 12and the shaft 10 is much larger than in the first example. With such arotor reaction vessel units can be centrifuged having a lateralextension with nearly the same centrifugal effect in all reactionvessels. The distance of the plate tray 11 to the rotation axis 18 ispreferably larger than the lateral extension of the reaction vesselunit, particularly at least 1.5 times or 2 times larger than the lateralextension of the reaction vessel unit.

Diametrically opposite to the receptacle section or plate tray 11, acounterweight 45 is fixed to the flanges 44 by means of further legs 46.A further plate tray could be provided instead of a counterweight 45,which is embodied for receiving a microtiter plate or a microtiter platecarrier together with a microtiter plate to form an adjustablecounterweight to the kind of microtiter plate used in the other platetray 11.

The opening 32 in the front side wall 25 is embodied at the level of thelowest position of the plate tray 11, which is the loading position ofthe rotor 8. The front platform 4 is provided on the same level as thebase wall 12 of the plate tray 11 in the loading position, so that amicrotiter plate or a microtiter plate on a microtiter plate carrier canslide from the front platform 4 onto the base wall 12 and vice versa,wherein the openings of the reaction vessels 3 of the microtiter plate 2are directed to the shaft 10. The opening 32 in the front side wall 25can be closed by an automatic door (not shown).

The centrifuge 1 comprises a motor 47 for driving the shaft 10 and thesame loading mechanism 33 as in the first example, wherein the flexibleelongated beam 34 is arranged with its free end 36 and magnetic element42 slightly above the level of the base plate 12 in the loading positionof the rotor 8 for loading and unloading a microtiter plate or amicrotiter plate on a microtiter plate carrier.

This centrifuge is designed for centrifuging a microtiter plate 2. Asthe distance between the microtiter plate and the shaft 10 or rotationaxis 18 is large, nearly the same centrifugal acceleration is exerted tothe fluid in the different reaction vessels 3. Therefore, the samecentrifugation effect is achieved independently of whether the fluid islocated in a center reaction vessel or a lateral reaction vessel.

A control unit is provided to control the speed as well as theacceleration of the rotor. The speed of the rotor is in the range of 100RPM to 3,000 RPM. The acceleration and deceleration of the rotor lies inthe range of 100-1,200 RPM/s. When starting the rotor, it shall beaccelerated, so that, after a turn of about 180°, at least a centrifugalacceleration of 1 g should be applied, so that no fluid drops out of thereaction vessels with its openings directing downwardly. Microtiterplates having deep well reaction vessels can be accelerated as fast aspossible. However, accelerating microtiter plates with small wells asreaction vessels could cause a contamination by sloshing of fluid fromone reaction vessel to a neighboring reaction vessel due to theacceleration. The danger of such a sloshing contamination depends on thefilling amount of the reaction vessels as well as on the form of thereaction vessels. It has been shown that with an acceleration up to 500RPM/s to 1,200 RPM/s, no contamination due to sloshing occurs.

A third example of a centrifuge 1 (FIG. 11-FIG. 12) is designed forcleaning and washing reaction vessel units as well as for centrifugingreaction vessel units. This centrifuge 1 is embodied similarly as theone of the first example. Similar parts of the centrifuge are designatedwith the same reference signs as in the first example.

The centrifuge 1 comprises a front platform 4, a centrifuge section 5and a driving section 6 (FIG. 12, 13).

The front platform 4 is coupled to a lifting means 48 to move the frontplatform 4 up and down, wherein the front platform 4 is kept in ahorizontal position. The opening 32 in the front side wall 25 is largerthan in the first example, so that it covers both the top most andlowest position of the plate tray 11 of the rotor 8. The front platform4 can be moved by means of the lifting means 48 between the top most andlowest position of the base wall 12 of the plate tray 11.

In the upper position, the front platform 4 is on the same level as thebase wall 12 in the uppermost position of the plate tray 11, so that amicrotiter plate or a microtiter plate on a microtiter plate carrier canbe slid horizontally from the front platform 4 onto the base wall 12 andvice versa. In the upper position of the front platform 4, the rotor isloaded or unloaded with a microtiter plate directed with its openingradially outwardly.

In the lower position, the front platform 4 is on the same level as thebase wall 12 of the plate tray 11 in the lowest position, so that amicrotiter plate or a microtiter plate on a microtiter plate carrier canslide from the front platform 4 onto the base wall 12 and vice versa. Inthis position, the plate tray 11 is loaded or unloaded with themicrotiter plate, wherein the openings of the microtiter plate aredirected radially inwardly or in a direction to the shaft 10. In theupper position, the rotor can be loaded with a microtiter plate forcleaning or washing reaction vessels, and in the lower position therotor can be loaded with a microliter plate for centrifuging the contentof the reaction vessels. This centrifuge is therefore calledhybrid-centrifuge because it is adapted for both cleaning and washingmicroliter vessels on one side and centrifuging the content ofmicrotiter plates on the other side.

The centrifuge 1 comprises two loading mechanisms 33, each having aflexible elongated beam 34 and a step motor 41 for actuating thecorresponding flexible elongated beam 34. Furthermore, a motor 47 isprovided for actuating the shaft 10 for revolving the rotor 8 around therotation axis 18. A dispensing bar 49 (FIG. 12) is provided adjacent tothe upper section of the opening 32 of the front side wall 25. Thisdispensing bar 49 comprises a plurality of dispensing nozzles 50arranged in line. For each reaction vessel in a column of the microtiterplate, a corresponding dispensing nozzle 50 is provided in thedispensing bar 49. The dispensing bar 49 is connected to a reservoir ofdispensing fluid, particularly washing fluid, and a pump, so that thedispensing fluid can automatically be dispensed via the dispensingnozzle 50 into the reaction vessels. The dispensing fluid can be keptheated in the reservoir. The dispensing of a heated washing solutionimproves the washing efficiency.

With the loading mechanism 33, each column of reaction vessels of amicrotiter plate can be individually arranged below the dispensing bar49 for dispensing fluid into the reaction vessels of the correspondingcolumn. With this dispensing bar integrated into the centrifuge, it ispossible to very quickly repeat several washing steps comprising acleaning or a washing step by centrifugation of the microtiter plate anda dispensing step in between the individual centrifugation steps.

The above described examples show centrifuges which are embodied forcleaning, washing, and/or centrifuging microtiter plates. FIGS. 14 and15 show a further example of a centrifuge for centrifuging gel cards.Gel cards are reaction vessel units having a plurality of reactionvessels which are arranged linearly side by side. Such gel cards havedeep wells.

The centrifuge 1 according to the fourth example comprises a centrifugehousing 51 which accommodates four centrifuge units, each comprising arotor 52 and an automatic lid 53 for individually opening and closingeach centrifuge unit. Each rotor 52 is individually driven by a motor(not shown), wherein the rotors 52 can be independently rotated.

Each centrifuging unit comprises a camera 54 for detecting the gel cards55, which is set in a corresponding rotor 52. The camera 54 comprises alight source.

For taking a picture, the rotation of the rotor is stopped and thecontent in the reaction vessels and the gel card is optically detectedand analyzed. The centrifugation can be continued after an opticaldetection and an optical analysis and these steps can be repeated againand again. Thus, it is possible to monitor the centrifugation effect onthe content in the reaction vessels without unloading the gel card ofthe centrifuge units.

In the preferred embodiment, the light source of the camera 54 is astroboscopic light source. The generation of flash lights with such astroboscopic light source is synchronized with the rotation of the rotorand the gel card, respectively, so that the flash light is generatedexactly when the gel card is in the field of vision of the camera 54. Inthe embodiment as shown in FIGS. 14 and 15, the field of vision of thecamera is disposed for detecting the gel card in the lowest position.Using such a stroboscopic light source allows arranging the camera andthe light source for detecting the gel card in any other rotationalposition, as a picture of the gel card can be taken without stopping therotation. Gel cards 55 consisting of a transparent plastic material arewell known in the art. Preferably, gel cards are used wherein one sideof the reaction vessels is colored and the other side of the reactionvessels is made of a transparent material. The color of the colored sideis preferably a light color, such as white or light grey. This coloredside can be embodied by a colored plastic material or a colored coatingwhich is applied on one side of the gel card. Such a gel card isoptically scanned on the transparent side, wherein the colored sideprovides a colored background. This colored background increases thecontrast, so that a reliable optical detection is possible even if theoptical power of the light source is rather weak. Such gel cards arepreferably used for blood testing, in particular typing of blood. Redagglutinations of blood can be detected with a high contrast in front ofa light, particularly white or grey, background. Such gel cards having acolored side form a separate inventive concept.

The fourth example shows a camera in the centrifuge for rotating gelcards. Such a camera can also be provided in a centrifuge in order tocentrifuge microtiter plates. In such a centrifuge, the camera and thecorresponding light source are located in the housing surrounding therotor and arranged with its field of vision, so that the picture of thebottom of all reaction vessels is taken when the openings of thereaction vessels are directed to the shaft of the rotor.

In all the above described examples, it is common that the reactionvessel units having reaction vessels with unclosed openings can behanded over to the centrifuge in their regular position with theopenings directed upwards so that liquid sample is kept safely in thereaction vessels. This makes it easy to integrate the centrifuge intoautomatic robots which comprise usually handling means for handling thereaction vessel units in their regular positions. In the fourth example,the gel cards can be loaded from the top into the receptacle sections ofthe corresponding rotors. In the first, second and third example, themicrotiter plates can be handed over to the front platform. Thehorizontal rotation axis makes it easy to hand over the reaction vesselunits in their regular positions. Furthermore, in the centrifugeaccording to the above described examples the reaction vessel units arealways held in an exactly defined position. There is no uncontrolleddegree of freedom, as it is the case in centrifuges having a swingingrotor. This defined position allows integrating further functions in thecentrifuge section, such as a camera (as described above) or a pipettingmeans. If a picture of the reaction vessels shall be takenautomatically, it is necessary that the position of the reaction vesselsis exactly known, even if the reaction vessels are rotating. Thecentrifuge according to the present invention can be further modified ifthe dispensing means are provided for dispensing a liquid into thereaction vessels when the reaction vessel units are located in the rotorof the centrifuge. For example, the second embodiment can be modified inthat the top portion of the jacket wall 24 is embodied as an automaticlid, wherein a dispensing bar comprising several dispensing nozzles islocated above the automatic lid. This allows to dispense washing fluidinto the reaction vessels without removing the reaction vessels from therotor. The centrifuges 1 for centrifuging microtiter plates can beprovided with a retractable dispensing bar which can be automaticallymoved in the section in between the plate tray 11 and the shaft when theplate tray is in its lowest position. Then it is possible toautomatically dispense reaction solutions into the reaction vesselslocated in the rotor 8, which can be further processed by centrifugingthe contact of the reaction vessel.

In the following, some examples of using a centrifuge according to thepresent invention are explained:

There is a strong need to improve the throughput in blood banks forblood typing. Usually, automatic blood typing is carried out by means ofgel cards. Such gel cards can be easily optically scanned and analyzed.However, the number of reaction vessels in such gel cards is limited, asthe reaction vessels are arranged linearly and not in a two-dimensionalarray as it is the case in microtiter plates.

A centrifuge 1 according to the second or third example can be used forblood typing by means of microtiter plates. The blood typing can becarried out by the following sequence of steps:

1. A certain amount of a gel is automatically filled into the reactionvessels of a microtiter plate by means of a dispenser.

2. The microtiter plate is placed on the front platform 4 of thecentrifuge 1. The microtiter plate is loaded into the plate tray 11 ofthe rotor 8 by means of the loading mechanism 33. The opening 32 of thefront side wall 25 is closed.

3. The microtiter plate is arranged in the rotor with its openingsdirected to the shaft or rotation axis, respectively. By rotating therotor 8, the content of the reaction vessels of the microtiter plate iscentrifuged so that the gel becomes free of air bubbles and settles downto the bottom of the reaction vessels very uniformly leading to theidentical filling height in each reaction vessel.4. The microtiter plate is unloaded from the rotor by means of theloading mechanism 33 and shifted onto the front platform 4.5. Sample material, e.g. one known type of red blood cells (RBCs) andone unknown type of red blood cells and corresponding reagents aredispensed into the reaction vessels 3 carrying the gel filling.6. The microtiter plate is automatically loaded into the rotor by meansof the loading mechanism 33, wherein the opening 32 is automaticallyopened and closed.7. The internal space of the centrifuge section is tempered for acertain period and a predetermined temperature so that the content ofthe reaction vessels of the microtiter plate is incubated. During theincubation step, two different types of blood samples are agglutinatingand, if the two blood samples are of the same type, they do not react.8. The microtiter plate is centrifuged. If the blood samples areagglutinated they remain on the surface or upper or radial inner sectionof the gel. If the blood samples do not react, the blood immerses intothe gel and reaches the lower or radial outer section of the gel.9. The microtiter plate is unloaded from the rotor to the front platformby means of the loading mechanism 33, wherein the opening 32 isautomatically opened. 10. The microtiter plate is put on an opticalscanner. The optical scanner scans the microliter plate with the fieldof vision from below and/or above. Non-reacting blood samples aredetected as red spots on the bottom of the reaction vessels. The top ofthe gel appears to be clear. Agglutinated blood samples will show adifferent pattern since agglutinated RBCs will remain as a dispersedpattern on the top of the gel. It has been shown that with opticaldetection with a field of vision from below, the blood types A, B and 0can be reliably detected and distinguished. The use of microtiter platesfor blood typing improves the throughput significantly and reduces thecosts in gel based blood tying by miniaturization and strongerparallelization.

This process is carried out with the centrifuge according to the secondor third example. Such a centrifuge is preferably provided with acamera, so that it is not necessary to move the microtiter plate on aseparate scanner. Cellular assays also demand washing steps in a verysimilar way like bead assays. Cells can be fixed to the surface ofmicroplates by centrifugation. Therefore, a hybrid system of thecentrifuge according to the third example that combines centrifugationand washing in subsequent steps of a cellular assay is advantageous. Thecell plate can be put onto the front platform which can be moved betweenan upper and a lower position. In the lower loading position the plateis loaded into the centrifuge, so that the plate is in a position thatthe openings of the plate are directed to the axis of the centrifuge andcells are spin down to the bottom of the plate where they can attach.Thereafter (e.g. after treatment with a drug) cells are washed in thesame instrument by moving the plate to the upper loading position of thecentrifuge with openings directed to the opposite of the rotor axis. Thehybrid system combines different steps of a workflow in one instrumentand is extremely useful for automation saving space in robotic systems.

Magnetic beads can be uniformly distributed in a solution in a reactionvessel. The magnetic forces are much stronger on the beads in the lowersection than in the upper section of the reaction vessel. Therefore itcan be appropriate firstly to centrifuge the reaction vessels containingthe beads (centrifuging step with the openings of the reaction vesselsdirected radially inwardly) and afterwards to wash the beads in thecentrifuge (washing step with the openings of the reaction vesselsdirected radially outwardly). This is particularly advantageous when adeep well microtiter plate is used, wherein the reaction vessels have aheight of 10 mm or more. With this method it is possible to use smalland light magnets in combination with deep wells for washing magneticbeads.

This procedure using a large collection volume is important, because thesensitive detection of virus nucleic acids in blood bank screening startwith high volumes.

Some experiments using magnetic beads 59 also comprise magnets like e.g.magnetic rods 57 to collect or hold the beads (FIG. 17). One example forsuch an experimental setup can further comprise a kind of a protectivecavity 58 for the magnetic rod in order to avoid any contact of the rodwith the sample liquid/reagent/buffer etc 60. By this the protrusion ofthe protective cavity can be placed within the sampleliquid/reagent/buffer etc. while the magnetic rod is put inside thecavity having no contact with the liquid. Due to the magnetic forcesworking through the cavity the magnetic beads will be hold on theprotrusion of the cavity at the opposite side of the rod.

The protrusions of the protective cavities have to be shaped in a waysuitable to enter the sample liquid or at least be close enough to thebeads to collect them by the magnetic forces through the cavity wall. Apossible protective cavity might for example be a kind of a negativecopy of the bead containing reaction vessel 3 or microplate. Theprotective cavity is complementary to the form of the magnetic rod sothat the rod can be tightly covered by the protective cavity. If theprotective cavity is put into the plate/reaction vessel containing thebeads and for example a magnetic rod is put inside the vessel of theprotective cavity the magnetic beads will be collected at the outsidelower part of the protective cavity. This unit comprising the protectivecavity and at least one magnetic rod, can be moved wherein the magneticbeads adhere to the outer surface of the protective cavity.

This method is used to transfer the bead together with the boundmaterial to a different plate for the next experimental step containingthe respective solution. However, together with the transfer of thebeads a residual amount of liquid will also be transferred from oneplate to the other. In cases of experiments with several transfer stepsthe amount of unwanted transferred liquid can sum up to highpercentages. In order to solve this problem the centrifuge according tothe invention can be used. For this the protective cavity together withthe magnetic rod holding the magnetic beads on the underside of thereaction vessel is transferred to a new empty plate and placed into thecentrifuge according to the invention (centrifuging step with theopening of the reaction vessel directed radially inwards).

By applying the proper centrifugation speed, the residual liquid 61 isremoved from the beads while the beads stay bound to the underside ofthe protective cavity due to magnetic forces. The respective speed hasto be adjusted depending on the employed magnets. After this step thewashing plate can be discarded and the protective cavity together withthe now dried beads can be transferred to the plate required for thenext experimental step.

Another experimental setup for which the centrifuge according to theinvention can be used is when a rod system is used to capture the targetmolecule (FIG. 18a-d ).

Thus, a further aspect of the invention are rods used for carryingreagents. These rods can also be used in manual operation or with arobot having a gripper for gripping such rods. A rod system comprisesrods 62 which can be magnetic or non-magnetic (FIG. 18a ). The design ofthe rods has to be in way to meet several technical requirements.

The diameter of the part of the rod, which will be placed in thereaction vessel 63, has to be adjusted to the diameter of the reactionvessel 64 (FIG. 18b ). The rods can be used for either single reactionvessels or for microtiter plates 65 with 96, 384 or more vessels.Therefor, the diameter of said rod part has to be smaller than one ofthe vessel but should not be too small to avoid staggering around of therod within the vessel.

Furthermore, the rod should not have any contact with the walls of thereaction vessel since this could lead to the removal of bound antibodies66 or antigens 67 on the rod. Therefore, the rod comprises a protrusion68, whereby the protrusion 68 is located above the rod part being withinthe vessel 63. This prevents the rod from further entering into thevessel and from touching the bottom part (walls or bottom) of thevessel. Said protrusion 68 can be shaped like a ring, for example, orcan just be one or more small protrusion(s).

The part of the rod being placed in the vessel 63 can be shaped in anyway fitting in the vessel. This can for example be cylindrical orconical. Further to increase the surface of this part of the rod it can,for example, be cross-shaped or star-shaped (FIG. 18d ). Other shapeslike vertical ridges or edges 69 are also suitable to increase thesurface of the rod.

The lower section of the rod placed in the vessel allows theimmobilization of reagents on the surface of the rod. This can beaccomplished by means of surface interactions like e.g. coating orcoupling. Alternatively, the rod can comprise a magnetic element, sothat reagents can be immobilized via magnetic beads on the surface ofthe rods. This lower section is called reaction section. Thereby the rodis made of a material allowing the coupling or coating of the rod withreagents, like e.g. antibodies or antigens.

The rods for these kinds of experiments can for example comprise amagnetic element. These magnetic rods are then used to capture beadscoated with, for example, antibodies. Also the direct coating ofnon-magnetic rods with, e.g., an antibody is possible.

In order to coat the rod with an antibody 66 or antigen 67 its surfacecan be modified accordingly, which is well known to a person skilled inthe art. The upper part of the rod 70, which is located above the vesselafter placing the rod within the vessel, is designed in a way that it ispossible to transfer the rod with a (standard) pipette tip 71 (FIG. 18c), which itself can be couple to a pipette (arm) coupling section. Apreferred design comprises a blind hole 72 on top of the rod of a sizethat a (standard) pipette tip 71 can be put in for a few millimeters,e.g., 1 to 12 mm. Depending on the tips used (e.g. from 1000 μl to 1 μl)the tip enters the blind hole 72 with different depth. When placing thetip 71 inside of the hole by pressure, the shaft of the tip should stickstronger to the pipette itself than the tip sticks in the hole of therod. Otherwise the tip would stay stuck in the rod.

In order to transfer the rod it is preferred that the hole is construedin shape of a tapered blind hole. Thereby, when placing the tip in thehole an airtight seal will be created by it. Once placed within the holethe pipette can generate a vacuum within the hole by sucking out the airby means of regular usage of the pipette. The vacuum will hold the rodon the pipette tip and it can be transferred to, e.g., the next reactionvessel. To release the rod the air is blown out by the regular pipettemechanism when blowing out any liquid. By reducing the vacuum the rodwill then be released from the pipette tips and can e.g., slide in thereaction vessel up to the point where the protrusion 62 will hold itback. Alternatively, the rod can be also gripped by means of a regulargripping device.

However, regular gripping devices commonly grip devices alongside. Thiscomes along with the need of space for the gripping device for everysingle device to be gripped. For placing rods in every single vessel ofa microplate a simultaneous gripping of rods for every vessel is barelyrealizable. According to the present mechanism by using the pipettestogether with the tips as gripping devices as many rods can be placed inreaction wells as many pipette tips are held by the pipette device. Alsosingle selected vessels on one plate can be used with the rod systemwhile others are left unused. The vessels can be filled with differentsample liquids in order to perform quick testing of several samples onone plate by using rods coated with the same or different antibodies orantigens.

After coating the rods or collecting the coated beads, the rods are thenplaced in the reaction vessel containing the corresponding sampleliquid.

When transferring the rod from one reaction vessel to the next(depending on the experiment many transfers might be required) thetransfer of residual sample liquid is undesired. Therefore, the rod canbe placed in an empty reaction vessel, which can be put in thecentrifuge according to the present invention. By a centrifugation stepwith the opening of the reaction vessel directed radially inwards theunwanted residual liquid can be removed easily from the rod beforetransferring it to the next reaction vessel.

By this, the amount of unwanted transferred residual liquid can bereduced enormously re-suiting in improved reaction conditions.

Regular gripping devices commonly grip devices alongside. This comesalong with the need of space for the gripping device for every singledevice to be gripped. For placing rods in every single vessel of amicroplate a simultaneous gripping of rods for every vessel is barelyrealizable. According to the present mechanism by using the pipettestogether with the tips as gripping devices as many rods can be placed inreaction wells as many pipette tips are held by the pipette device. Alsosingle selected vessels on one plate can be used with the rod systemwhile others are left unused. Commonly used pipette robots can carry amaximum of 96 standard pipette tips. This number is limited due toreaction well size and the diameter of the pipette tip at its upper endwhere it is coupled to the pipette device. There are pipette armscarrying more than 96 tips, e.g. 384, however, these are employingspecial tips, which are expensive. In order to handle the rods disclosedherein in higher numbers than 96 either expensive special tips have tobe employed or, since the design of these rods allows the handling withnormal prized standard pipette tips and standard pipetting head with 96channels, the rods just need to be moved four times in order to fill acomplete 384 vessel plate with 384 rods. These steps, however, do notneed much time and, thus, do not slow down the experimentation processin a significant manner. The rods can be moved in a staggered way toplace a rod in every second vessel of a 384 plate, for example. Even thehandling of more than 384 rods for plates with more vessel can berealized and only requires the adaption of the rod size in accordancewith the vessel size.

The rods disclosed herein can controllable be gripped and released ofthe reagent carrier units with an ordinary liquid handler. Any lipidhandler can be used. There is no need to mechanically adapt the liquidhandler for enabling it to handle also reagent carrier units. Devices,which are embodied for pipetting any kind of liquids are well known to aperson skilled in the art. These kinds of devices are also called liquidhandler. The most common liquid handlers are pipettes or robot arms forpipetting fluids.

Thus, the rods and their convenient way of handling via pipette tipsallow a fast handling of high numbers of rods, which can be automatedeasily without additional costs for special tips or pipette devices.

Amplification reactions of nucleic acids typically require hightemperatures (like PCR). They are carried out in high throughput inmicrotiter plates. In order to prevent evaporation of single reactionvolumes plate sealers are used to fix a foil on top of the microtiterplate. It is costly and difficult to integrate plate sealers intoautomatic labor robotic systems. Instead of the foil mineral oil hasbeen used to cover the reaction in the early days of PCR. A robot caneasily handle the mineral oil but small quantities of aqueous solutionsand small quantities of mineral oil might be difficult to be dispensedto form two separate phases (oil on top) in microtiter plates with highperformance. A centrifugation step is needed to separate the phases andmake 100% sure for all reactions that coverage is successful and noaqueous volume will evaporate. The centrifuge is easy to integrate inrobotic workflows as described above. List of references

List of references 1 centrifuge 43 leg 2 microtiter plate 44 flange 3reaction vessel 45 counterweight 4 front platform 46 leg 5 centrifugesection 47 motor 6 driving section 48 lifting means 7 rim 49 dispensingbar 8 rotor 50 dispensing nozzle 9 housing 51 centrifuge housing 10shaft 52 rotor 11 plate tray 53 lid 12 base wall 54 camera 13 U-rail 55gel card 14 base shank 56 rotor space 15 side shank 57 magnetic rod 16side shank 58 protective cavity 17 central bore 59 magnetic beads 18rotation axis 60 sample liquid/reagent/ buffer etc. 19 stopper 61residual liquid removed from cavity beads 20 microtiter plate carrier 62rod 21 rim 63 lower part of the rod 22 coupling element 64 reactionvessel 23 housing 65 microtiter plate 24 jacket wall 66 antibody 25front side wall 67 antigen 26 rear side wall 68 protrusion 27 lower halfshell 69 ridges/edges 28 upper half shell 70 upper part of the rod 29flange 71 schematic depiction of a pipette tip 30 drain 72 blind hole 31support 32 opening 33 loading mechanism 34 flexible elongated beam 35inner wall 36 free end 37 upper strand 38 lower strand 39 wheel 40 wheel41 stepper motor 42 magnetic element

The invention claimed is:
 1. A centrifuge for cleaning a reaction vesselunit that includes at least one opening, comprising: a housing includinga cylindrical inner surface and a drain; a rotor disposed within thehousing and including an outmost surface, the rotor being configured tohold the reaction vessel unit with its at least one opening directedoutwardly; a motor for rotating the rotor around a rotation axis in afirst rotational direction to cause liquid from the reaction vessel tobe expelled from the at least one opening onto the inner surface of thehousing; wherein a gap is provided between the inner surface of thehousing and the outmost surface of the rotor, a size of the gap beingsuch that by rotating the rotor a wind is generated which drives theexpelled liquid on the inner surface of the housing to the drain; andwherein a size of the gap is not less than 0.3 mm.
 2. The centrifugeaccording to claim 1, wherein a size of the gap is not more than 1 mm.3. The centrifuge according to claim 1, wherein a rotation speed of therotor is at least 500 RPM.
 4. The centrifuge according to claim 1,wherein a rotation speed of the rotor is at least 1,500 RPM.
 5. Thecentrifuge according to claim 1, wherein a rotation speed of the rotoris in a range of 5-3,000 RPM.
 6. The centrifuge according to claim 1,further comprising a control unit connected to the motor to controlrotation of the rotor, wherein the control unit is configured to controla rotation speed of the rotor based on the surface tension of a liquidin the reaction vessel unit and the gap between the inner surface of thehousing and the outmost surface of the rotor.
 7. The centrifugeaccording to claim 1, further comprising a control unit connected to themotor to control rotation of the rotor, wherein the control unit isconfigured to reverse a rotational direction of the rotor at an end of acentrifuging step so that a liquid film on the inner surface on a rearside of the drain with respect to the first rotational direction isdriven into the drain by rotating the rotor with a second rotationaldirection.
 8. The centrifuge according to claim 1, wherein the reactionvessel unit comprises a magnetic material and wherein the rotorcomprises a magnetic coupling element for holding the reaction vesselunit.
 9. The centrifuge according to claim 8, wherein the rotor includesa rear side along the rotation axis, and wherein the magnetic couplingelement comprises a stopper at the rear side of the rotor.
 10. Thecentrifuge according to claim 1, further comprising an aspiration pumpconnected to the drain for discharging the expelled fluid.
 11. A systemfor cleaning a reaction vessel unit, comprising: a centrifuge accordingto claim 1; and at least one reaction vessel unit comprising a pluralityof reaction vessels which are arranged in a two-dimensional array;wherein each of the reaction vessels includes an opening; and whereinthe rotor of the centrifuge holds the at least one reaction vessel unitwith each opening directed outwardly.
 12. A method for cleaning areaction vessel unit with a centrifuge, wherein the reaction vessel unitcomprises at least one opening and wherein the centrifuge comprises ahousing including a cylindrical inner surface and a drain, a rotordisposed within the housing and including an outmost surface, and a gapbetween the inner surface of the housing and the outmost surface of therotor, the method comprising the steps of: loading the reaction vesselunit into the centrifuge so that it is held by the rotor with its atleast one opening directed outwardly; and centrifuging the reactionvessel unit by rotating the rotor in a first rotational direction,wherein the centrifuging causes liquid in the reaction vessel unit to beexpelled onto the inner surface of the housing, and wherein a size ofthe gap and a rotation speed of the rotor are such that centrifuginggenerates a wind which drives the expelled liquid on the inner surfaceof the housing to the drain, wherein the centrifuging is performed witha gap not less than 0.3 mm.
 13. The method according to claim 12,wherein the centrifuging is performed with a gap not more than 1 mm. 14.The method according to claim 12, wherein the centrifuging is performedat a rotation speed of at least 500 RPM.
 15. The method according toclaim 12, wherein the centrifuging is performed at a rotation speed ofat least 1,500 RPM.
 16. The method according to claim 12, wherein thecentrifuging is performed at a rotation speed of in a range of 5-3,000RPM.
 17. The method according to claim 12, wherein the method furthercomprises the step of: reversing a rotational direction of the rotorafter the step of centrifuging so that a liquid on the inner surface onthe rear side of the drain with respect to the first rotationaldirection is driven into the drain by rotating the rotor in a secondrotational direction.
 18. The centrifuge according to claim 1, whereinthe inner surface of the housing has a lower section below the rotationaxis, and wherein the drain is formed in the lower section of the innersurface of the housing.
 19. The centrifuge according to claim 1, whereinthe drain comprises a groove in the inner surface of the housing. 20.The centrifuge according to claim 19, wherein the groove is parallel tothe rotation axis of the rotor.